Quantitative NMR Spectroscopy

Quantitative NMR Spectroscopy

Quantitative NMR Spectroscopy is a universal and quantitative analytical technique. Being a unique structural tool, but it can also be used for accurate quantitative measurement with properly designed experiments. NMR also competes with metrological techniques for purity determination and reference material analysis. We have found that quantitative NMR is a valuable tool for assay determination, i.e., accurate purity measurements of pharmaceutical reference standards. Offering an unbiased view of the sample composition, and the possibility to simultaneously quantify multiple compounds. Quantitative NMR (qNMR) uses the data from a nuclear magnetic resonance spectrum, namely the area or integral of an NMR peak, to determine the concentration of a molecule in solution.

NMR-based metabolomic studies, dedicated to both the characterization of herbal remedies and clinical diagnosis, have increased considerably. The integral is proportional to the number of nuclei from the corresponding signal. NMR has the inherent advantage of providing simultaneous access to both qualitative and quantitative information. It is necessary that the compound has an NMR-active nuclitide, which is specific to the analyte of interest. Quantitation can be achieved by making use of either an external or an internal calibration standard. The signal intensity is directly proportional to the number of nuclei that give rise to a specific resonance.

Quantitative NMR has been used to simplify the overall purity determination of reference materials. qNMR can be an alternative to the mass balance method by measuring the amount of analyte directly. Measurements are at least as reliable and precise as those obtained by the more commonly used chromatography-based techniques. For use in a quantitative NMR, an internal calibration standard is chosen that is appropriate to the assay determination. This advantage is particularly useful for metabolomic studies, which represent a second major application of qHNMR. The internal standard must also possess adequate solubility.